“…In addition, the well-known studies (e.g., Ellis, Bessemer, Devine, & Trafton, 1962) related to acquired equivalence of cues and acquired distinctiveness of cues indicate that learning different labels to stimuli will make the stimuli functionally distinctive and that learning the same label to these stimuli will make them functionally similar. Relevant labels, that is, labels with characteristics similar to the defining qualities of the concept, result in enhanced discrimination of appropriate cues, especially where stimuli are low in meaningfulness (Pfafflin, 1960;Ranken, 1963). Where labeling is not coordinate with the transfer task, pretraining with labels for selected stimulus 1 The research reported in this paper was supported in part by the Advanced Research Projects Agency (ARPA Order No.…”